oral solution?

what is the best method of making an oral PH solution? PEG-400 only method or the olive oil/BA method? i want to get a decent dosage (i.e. 5mg/ml atleast) when making an mdien or m4ohn solution. i know that will most likely need to bake the stuff, but which is shown to be more stable? please forgive the newb question, but im new to this...